1. Field of the Invention
This invention generally relates to a facility for receiving nuclear waste of various radiation levels in shipping containers and solidly over-packing this waste into a module having a sufficiently low surface radiation count so that the wastes may be safely handled by human workers and permanently buried at a waste disposal site.
2. Description of the Prior Art
Systems for packaging nuclear waste are known in the prior art. In the earliest of these systems, such wastes were merely packed on site into 55-gallon steel drums. The drums were then transported to a remote burial site. The surface radiation of these drums was often too high to allow them to be handled by human workers; consequently, the drums were handled by long boom cranes, which dropped the drums into simple trenches, where they were buried. Such systems were known as "kick and roll" systems. Unfortunately, such "kick and roll" systems proved to be unsatisfactory for the land disposal of nuclear wastes. The loose soil which these trenches were filled in with was much more permeable to water than the densely-packed soil which formed the trench sides, or the dense rock strata which typically formed the trench bottom. The permeability of the loose soil surrounding the drums caused these trenches to collect large amounts of standing water in what is known as the "bathtub effect". This standing water ultimately caused the steel walls of the drums buried within these trenches to corrode and collapse. The collapsing drums and compaction of the soil over time resulted in a downward movement or subsidence of the soil which caused a depression to form over the top of the trench. This depression in turn collected rain and other forms of surface water and hence worsened the tendency of the trench to collect and maintain a pool of standing water over the drums. The increase in standing water resulted in still more soil subsidence, and accelerated the corrosion and collapse of the drums buried therein. The corrosion and collapse of the drum containers in such sites has resulted in some radioactive contamination of the ground water flowing through them.
To solve the problems associated with such "kick and roll" packaging and disposal systems, packaging systems utilizing radiation-shielding concrete packages were developed. In contrast to the thin walls of the 55-gallon drums, the thick walls of these concrete packages reduced the surface radiation of the resulting package to a point where they did not have to be handled by long-boom cranes. Instead, they could be safely handled by human operators. Additionally, the thick layer of concrete was much more resistant to degradation from ground water. In use, these thick-walled concrete packages were carried to the sites where the waste was generated, which was typically a nuclear power plant. The waste was thrown directly into the interior of these packages, and the packages were sealed on-site at the nuclear plant. The sealed packages were then carried to a remote disposal site and buried. The low surface radiation associated with these concrete packages allowed them to be stacked in an orderly fashion within the burial trench along with wastes in other containers by shielded forklifts.
Unfortunately, despite the superiority of such concrete packaging over the drum-type packaging used in "kick and roll" systems, there are still a number of shortcomings associated with this particular packaging system. First, the packaging of the waste at the nuclear power plant for burial at a remotely-located disposal site required a great expenditure in time and effort in transporting the heavy concrete packages to and from the site. Second, the unisolated processing of the waste at the nuclear power plant exposed the plant to the possibility of nuclear contamination if any mishaps occur during the on-site packaging process. Third, there was no provision in such a system for determining whether or not any of the waste dumped into the concrete package was in liquid form. Federal regulations now strictly prohibit the burying of any waste in liquid form; therefore, the inability to quickly and conveniently confirm that none of the wastes loaded into the package are in liquid form is important. Fourth, this system could not conveniently handle high-level wastes, such as spent control rods; the concrete walls of the packages were simply not thick neough to reduce the surface radiation of the package to an acceptable level. Finally, the surface radiation of the concrete packages varied depending on the activity of the particular wastes packed therein; this system had no provision for conveniently confirming that the surface radiation of the resulting package did not exceed the maximum safe level at which the package could be directly handled by human workers.
Clearly, a need exists for a packaging system which is capable of packaging radioactive waste of contactable and non-contactable levels of radioactivity into modules whose surface radiation does not exceed that which can be safely handled by human operators. Ideally, such a packaging system would cut to a minimum the amount of transportation of heavy packages, and should have some sort of means for preventing the radioactive contamination of the surrounding area should any mishaps occur during the packaging process. Finally, such a system should be capable of determining whether or not any liquids are present in the waste.